Roof for land vehicles, especially railway cars, and method of making the same



Aug. 3, 1954 BARNES' ET AL 2,685,263

A ROOF R LAND VEHICLES, ESPECIALLY RAILWAY D METHOD OF MAKIN THE SAME Aug. 3, 1954 BARNES ET AL 2,685,263 ROOF FOR LAND VEHICLES, ESPECIALLY RAILWAY v ARS. AND METHOD OF MAKING THE SAME Filec i July 14, 1948 y 4.Sheets-Shet 2 Patented Aug. 3, 1954 R OOF FOR LAND VEHICLES, ESPECIALLY RAILWAY CARS, AND METHOD OF MAK- ING THE SAME Gladeon M. Barnes,

Philadelphia, Charles L. Fke, Ardmore, and Albert G. Dean,

Narberth, Pa.,

assignors to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Application July 14, 1948, Serial No. 38,726

6 Claims.

This invention relatos to a roof for land vehicles, especially railway cars, and method of making the same, and has for an object the provision of improvements in this art.

The invention is related to that disclosed in the copending application of Albert G. Dean, assigned to a common assignee, and entitled Body for Land Vehicles, Espeoially Railway Cars and Method of its Assembly, now Patent 2,619,045, issued November 25, 1952.

It has been found that when the roof of a land vehicle, made of a thin metal skin sheet supported by longitudinal frame members and trans verse carlines, is exposed to strong sunlight, the thin metal sheet or skin will develo buckles or Waves. This is especially noticeable near the center of the car length, the car being supported near its ends. When as is usual, the car roof is quite flat with a large radius of curvature in the center and more sloping with a small radius of curvature toward the edges which merge into the vertical side walls of the car, the buckling is more noticeable in the flat top portion of the roof. These wrinkles are objectionable in appearance; and when the skin sheets constitute strength elements in the structure, the wrinkles are objectionable from a stress standpoint.

According to this invention the top roof skin sheets are put into a state of pretension longitudinally by precompressing the longitudinal r frame members, attaching the skin sheets while the longitudinals are so compressed, and then releasing the longitudinals from the compressing force. This avoids cutting waste ends off the skin sheets, as would be required if they were gripped at the ends and stretched, permits the use of simple apparatus, and provides other advantages. To avoid leaving the transverse frame members in a bent condition, their ends not being in the region of prestress at the top of the car, the transverse frame members are attached to the longitudinal elements before the final stage of prestressing and are thus first bent from straight dispositicn so that they will bend back to straight position when the prestress is relieved.

In the drawings, which llustrate a selected structure as effected by the several steps of the method:

Figure 1 is a perspective view of a railway car roof in an intermediate stage of construction where the present prestressing method begins, the top longitudinal frame members being laid on but not attached;

Figure 2 is a similar perspective view of a roof structure which is completed except for the closing sheets;

Figure 3 is a transverse section through a completed roof;

Figure 4 is a diagrammatic side elevation of a roof structure with partial prestress applied, a structure somewhat shorter than that of Fig. 1 being shown to avoid breaking away the center portion of the view;

Figure 5 is a transverse section through the structure in its jig to show the longitudinal and transverse frame members temporarily held to gether by clamps;

Figure 6 is a view similar to Fig. 4 but With full prestress applied;

Figure 7 is a view similar to Fig. 4 but with the skin sheets at the top attached and the prestressing load removed;

Figure 8 is a top plan view of Fig. 7; and

Figure 9 is a section in the J'ig with the structure complete except for closing sheets.

The structure shown, here a railway car roof, comprises carlines lll, purlines Il, end plates l2, sleepers or side chord members l3, skirts, upper side panels, or letter boards H, molding rails I5 and IS, top corrugated skin sheets l8a to 82' inclusive, curved side sheets l9.a, I9b, closing sheets 20a, 20b, and skirt cover sheets 2la, 2 lb.

The combined top sheets [8a to l8i in an exemplary structure have approximately the same strength within the prestress limits as the two purlines ll and for the same load will elongate approximately the same amount as the purlines will shorten. If made of the samematerial, the combined cross sectional area of the top skin sheets will be approximately the same as that of the two purlines combined. The material of both may be cold rolled 18-8 stainless steel, for example.

At the beginning of operations, the chord members 13 are secured in a jig 25, as shown in Fig. 5, and the carlines are connected at their lower ends, as by welding, to the chord members. They will, of course, be thus secured while held in verti cal planes. The letterboards M may be connected at this or some later stage.

After the carlines have been secured at their lower ends, the purlines l l are placed in position and may be welded to the center carline or to several carlines adjacent the center. This may be done without harm because subsequent movements of the purlines near the center of their length will be so small as to be negligible, hence the amount by which the carlines will be thrown out of vertical planes will be negligible. Tension rods or bars 3|.I are assembled with or adjacent the purlines, preferably within them when they are channel-shaped as shown, and blocks 3| and nuts 32 are placed on the rods to apply compression loads to the purlines. If the purllnes tend to buckle, they may be temporarily held to the carlines from place to place, as by C-clamps 33.

Assuming that the top sheets and purlines are of equal extensibility for equal loads, there will first be applied a preloading equal to half of the total precompression which is to be given the purlines. The carlines are now after this first stage all attached to the purlines. The end sheets may also be attached at several places but not in such manner as to be deformed by later operations. As the carlines are progressively attached permanently to the purlines, the temporary clamps are removed before attachment to permit the carlines to have a vertical position when attached.

After the carlines and purlines have been connected together, the purlines are further loaded by the rods and nuts until the total desired precompression is achieved, as shown in Fig. 6. The top skin sheets are now applied and they are attached to the frame, at least at or near the ends. They may also be attached, if desired, at or near the center. Since the total movements are small, being for example about one-quarter inch for an eighty foot length, no harm will result if the skin sheets are welded to the carlines and purlines throughout their extent at this stage. In the diagrams the positional changes are exaggerated for clarity of illustration.

After the skin sheets have been attached, the nuts on the load-applying rods are turned off to remove the externally applied load. However, as the purlines reexpand in length the skin sheets will be prestressed in tension and this will continue until the pretension in the skin sheets balances the precompression in the purlines. When of equal strength, as assumed for simplicity, this balance will occur when the purlines have expanded for half the total length of their compression, thus bringing all the carlines back into vertical planes again.

After release, the curved skin sheets l9a, l9b and the closing sheets 20a, 2Gb may be attached. Since the movements are small and curved sheets do not readily wrinkle, these other sheets may oe applied before the external loading is removed, that is, when the top sheets are attached.

It is thus apparent that an improved structure and an improved method of fabrication have been provided. By prestressing only the top of the structure where the sunshine directly strikes and causes most expansion While leaving the lower parts without prestress, the top can take full heat expansion without wrinkling or buckling. The prestress takes care of a temperature differential of approximately 50 F. The top skin sheets also form strength elements in the composite structure. The method of assembly secures a true and dependable structure with a minimum of labor and material.

As an example of sizes involved, the car may be 85 feet long and have a span between truck supports of about 60 feet, roof skin sheet of .02 inch thickness, top center curvature radius about 10 feet, side curvatura radius about 20 inches, carline section thickness about .06 inch and purline sectional thickness .075 to .125 inch.

While one embodiment of the invention has been described in detail for purposes of illustration, it is to be understood that there may be various embodiments within the range of the invention.

What is claimed is:

1. The method of making a land vehicle roof which includes full-length longitudinal metal skin sheets and a metal frame formed of fulllength longitudinal members and upwardly bowed transverse members, which method comprises the steps of applying an endwise precompressing force to the top longitudinal frame members While holding them against buckling, attaching the precompressed longitudinal frame members to the intermediate top portion of the length of the bowed transverse frame members, holding the ends of the transverse frame members in a fixed position and further precompressing the top longitudinal frame members endwise, some of the transverse frame members being bent sidewise by movement of their attached portions with the longitudinal frame members, attaching the longitudinal skin sheet in smooth unstressed condition to the frame at the top in the zone of the precompressed longitudinal frame members, and relieving the longitudinal frame members from the precompressing force, whereby the top longitudinal frame members re-expand and put tenson in the skin sheet and bring the transverse frame members back into the shape which they had when they were attached to the longitudinal frame members.

2. The method of making a land vehicle roof which includes full-length longitudinal metal skin sheets and a metal frame formed of fulllength purlines and upwardly bowed carlines, which method comprises the steps of applying an enclwise compressing force to the purlines at the top of the roof while holding them against buckling, attaching the precompressed purlines to the top portion of the carlines, holding the ends of the carlines in fixed position and further precompressing the top purlines endwise, the attached top portion of the carlines being bent sidewise where the top purlines move endwise, attaching the top longitudinal skin sheet in smooth unstressed condition to the frame at the top in the zone of the precompressed purlines, relieving the precompressing force from the top purlines to cause them to reexpand against the skin sheet to put tension in the skin sheet and substantially remove the sidewise bending from the carlines, and then applying the skin sheets to the remaining portions of the roof frame.

3. Ihe method of making a land vehicle roof which includes fulllength longitudinal metal skin sheets and a metal frame formed of fulllength purlines, upwardly bowed carlines and vertical side panels at the lower ends of the carlines, the carlines having a relatively straight horizontal top mid-portion, curved side-portions and straight vertical lower end portions, which method comprises the steps of applying an endwise compressing force to the purlines at the top of the roof while holding them against buckling, attaching the carlines to the side panels at their lower ends and to the top purlines in their straight top mid-portions, applying further endwise compressing force to the top purlines, the attached top portion of the carlines being bent sidewise where the top purlines move endwise, attaching the top longitudinal skin sheet in smooth unstressed condition to the frame at the top in the region of the precompressed purlines, relieving the precompressing force from the top purlines to cause them to re-expand against the skin sheet to put tension in the skin sheet and substantially remove the sidewise bending from the carlines, and then applying the skin sheets to the remaining portions of the roof frame.

4. In a land vehicle body, a roo-f unit formed of a metal frame and a thin metal skin sheet which is constructed in such manner as to avoid skin wrinkling due to sun heat and to have the correct shape at the lower edges to fit with body side portions, said roof unit comprising longitudinal metal frame members, transverse upwardly bowed metal frame members and a longitudinal metal skin sheet, the longitudinal frame members and skin sheet in the top portion of the roof being in a longitudinally opposed endwise stressed state of compression and tension respectively, and the frame members and skin sheets on the sides being in a non-stressed state.

5. In a land vehicle body, a roof unit formed of a metal frame and a thin metal skin sheet which is constructed in such manner as to avoid. skin Wrinkling due to sun heat and to have the correct shape at the lower edges to fit with body side portions, said roof unit comprising longitudinal metal frame members, a longitudinal metal skin sheet, and transverse metal frame members which are relatively straight and horizontal at the top, curved on the sides and straight and vertical at the lower ends, the longitudinal frame members and skin sheet in the top porti0n of the roof being in a longitudinally opposed endwise stressed state of compressi0n and tension respectively, and the frame members and skin sheets at the curved sides and bottom ends bein in a nonstressed state.

6. In a land vehicle body, a roof unit formed of a metal frame and a thin metal skin sheet which is constructed in such manner as to avoid skin wrinkling due to sun heat and to have the correct shape at the lower edges to fit with the body side portions, said roof unit comprising a plurality of longitudinally spaced metal carlines which have 1elatively straight portions at the top and at the lower ends and curved portions on each side between the straight portions, longitudinal metal frame members near the lower ends of the carlines and at each end of the top straight portion, leaving the curved porti0ns of the carlines without longitudinal members, a longitudinal metal skin sheet disposed between the spaced top longitudinal frame members, the top skin sheet and frame being in longitudinal stress against each other and so connected together, and longitudinal metal skin sheets in unstressed condition covering the other portions of the roof.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,549,251 Geyer Aug. 11, 1925 1,727,681 Thompson et al. Sept. 10, 1929 2,039,398 Dye May 5, 1936 2,110,752 Wright Mar. 8, 1938 2,314,979 Gunn Mar. 30, 1943 2,342,025 Watter Feb. 15, 1944 2,354,494 Upson Dec. 15, 1944 2,441,858 Watter May 18, 1948 

